<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Div</title>

  <style>
    body {
      margin: 0;
      padding: 0;
    }
    #header {
      background-color: red;
      height: 80px;
      width: 100%;
    }
    #section {
      background-color: green;
      height: 800px;
      width: 100%;
    }

    #left {
      background-color: pink;
      height: 800px;
      width: 250px;
      float: left;
    }

    #right {
      background-color: yellow;
      height: 800px;
      width: 250px;
      float: right;
    }

    #footer {
      background-color: aquamarine;
      width: 100%;
      height: 100px;
    }
  </style>

</head>

<body>

<!-- div-->
<div id="header">header</div>

<div id="section">section
  <div id="left">left</div>
  <div id="right">right</div>
</div>

<div id="footer">footer</div>

</body>
</html>